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Encyclopedia > Coaxial cable
Coaxial Cable

Coaxial cable is an electrical cable consisting of a round conducting wire, surrounded by an insulating spacer, surrounded by a cylindrical conducting sheath, usually surrounded by a final insulating layer (jacket). It is used as a high-frequency transmission line to carry a high-frequency or broadband signal. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Coaxially mounted weapons refer to those weapon systems that are mounted coaxially, side-by-side, with the main weapon system. ... 6 or 15cm outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. ... This article or section is in need of attention from an expert on the subject. ... A right circular cylinder An elliptic cylinder In mathematics, a cylinder is a quadric surface, with the following equation in Cartesian coordinates: This equation is for an elliptic cylinder, a generalization of the ordinary, circular cylinder (a = b). ... A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... Broadband in telecommunications is a term which refers to a signaling method which includes or handles a relatively wide range of frequencies which may be divided into channels or frequency bins. ... The electromagnetic field is a physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. ... In science and engineering, conductors, such as a electrical connector, are materials that readily conduct electric current through electrical conduction. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...

Coaxial cables may be rigid or flexible. Rigid types have a solid sheath, while flexible types have a braided sheath, usually of thin copper wire. The inner insulator, also called the dielectric, has a significant effect on the cable's properties, such as its characteristic impedance and its attenuation. The dielectric may be solid or perforated with air spaces. Connections to the ends of coaxial cables are usually made with RF connectors. coaxial cable In geometry, coaxial means that two or more forms share a common axis; it is the three-dimensional linear analog of concentric. Coaxial cable, as a common example, has a wire conductor in the center (D) a circumferential outer conductor (B) and an insulating medium called the dielectric... A braid Step by step creation of a basic braid using three strings To braid is to interweave or twine three or more separate strands of one or more materials in a diagonally overlapping pattern. ... For other uses, see Copper (disambiguation). ... This article or section is in need of attention from an expert on the subject. ... A dielectric, or electrical insulator, is a substance that is highly resistant to electric current. ... The characteristic impedance of a uniform transmission line is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. ... Attenuation is the reduction in amplitude and intensity of a signal with respect to distance traveled through a medium. ... An RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range. ...

A: outer plastic sheath
B: copper screen
C: inner dielectric insulator
D: copper core

Photo of RG-59 cable, taken and annotated by Heron 20:15, 6 Oct 2004 (UTC). ... Photo of RG-59 cable, taken and annotated by Heron 20:15, 6 Oct 2004 (UTC). ...

Signal propagation

The outer conductor can also be made of (in order of decreasing leakage and in this case degree of balance): double shield, wound foil, woven tape, braid. The ohmic losses in the conductor increase in this order: Ideal conductor (no loss), superconductor, silver, copper. It is further increased by rough surface (in the order of the skin depth, lateral: current hot spots, longitudinal: long current path) for example due to woven braid, multistranded conductors or a corrugated tube as a conductor) and impurities especially oxygen in the metal (due to a lack of a protective coating). Litz wire is used between 1 kHz and 1 MHz to reduce ohmic losses. Coaxial cables require an internal structure of an insulating (dielectric) material to maintain the spacing between the center conductor and shield. The dielectric losses increase in this order: Ideal dielectric (no loss), vacuum, air, PTFE-foam, PTFE, polyethylene. It is further increased by impurities like water. In typical applications the loss in polyethylene is comparable to the ohmic loss at 1 GHz and the loss in PTFE is comparable to ohmic losses at 10 GHz. A low dielectric constant allows for a greater center conductor: less ohmic losses. An inhomogeneous dielectric needs to be compensated by a noncircular conductor to avoid current hot-spots. Litz wire is a special type of wire used in electronics. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... This article does not cite any references or sources. ... Ohms law, named after its discoverer Georg Ohm [1], states that the potential difference (or voltage drop V) between the ends of a conductor (for example, a resistor R) and the current, (I) flowing through R are proportional at a given temperature: where V is the voltage and I... Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. ...

Connectors

Main article: RF connector
Coaxial connectors

One increasing development has been the wider adoption of micro-miniature coaxial cable in the consumer electronics sector in recent years. Wire and cable companies such as Tyco, Sumitomo Electric, Hitachi Cable, Fujikura and LS Cable all manufacture these cables, which can be used in mobile phones. Tyco has been used as the name for a number of distinct companies: Tyco International is a Bermuda-based conglomerate. ... The Sumitomo Group is a group of related japanese companies, (keiretsu). ... Hitachi Cable, Ltd. ... LS Cable of South Korea was founded in 2005 with the split off of parts of the LG Cable conglomerate. ...

Important parameters

Schematic representation of a coaxial transmission line, showing the characteristic impedance Z0.
• The characteristic impedance in ohms (Ω) is calculated from the ratio of the inner (d) and outer (D) diameters and the dielectric constant (εr). The characteristic impedance is given by $Z_0=frac {138}{sqrt{epsilon_r}}timeslog(frac {D} {d})$. Assuming the dielectric properties of the material inside the cable do not vary appreciably over the operating range of the cable, this impedance is frequency independent.
• Capacitance, in farads per metre.
• Resistance, in ohms per metre.
• Attenuation or loss, in decibels per metre. This is dependent on the loss in the dielectric material filling the cable, and resistive losses in the center conductor and shield. These losses are frequency dependent, the losses becoming higher as the frequency increases. In designing a system, engineers must consider not only the loss in the actual cable itself, but also the insertion loss in the connectors.
• Outside diameter, which dictates which connectors must be used to terminate the cable.
• Velocity of propagation, which depends on the type of dielectric.
• Cutoff frequency

Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... The characteristic impedance of a uniform transmission line is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. ... The ohm (symbol: Î©) is the SI unit of electric resistance. ... The relative dielectric constant of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... Examples of various types of capacitors. ... â€¹ The template below (Unit of length) is being considered for deletion. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... For other uses, see Decibel (disambiguation). ... Look up engineer in Wiktionary, the free dictionary. ... In telecommunication, the term insertion loss has the following meanings: 1. ... An RF connector is an electrical connector designed to work at radio frequencies in the multi-megahertz range. ... Velocity of Propagation (VoP) is a parameter that characterizes the speed at which an electrical or radio signal passes through a medium. ... A bode plot of the Butterworth filters frequency response, with corner frequency labeled. ...

Leakage

Leakage is the passage of electromagnetic fields through the shield of the cable. An ideal shield is a solid metal tube of perfect conductivity, perfectly sealed to the connectors at either end. Since no electric field can exist inside a perfect conductor, and a radiating electromagnetic field cannot exist without its electric component, it follows that no electromagnetic radiation can pass through a perfect conductor. Image File history File links Emblem-important. ...

Real cables have a shield made of an imperfect, although usually very good, conductor that inevitably contains some holes. It is possible to measure small voltages on the inside of the shield caused by normal electromagnetic fields outside the shield, and very high voltages in the extreme case when a nuclear weapon is detonated outside the shield. By these means, a typical leakage of 90 dB has been measured. This leakage occurs at holes in the shield, or in case of poor contact between connectors at either end of the cable, or within the circuitry between the cable and the radio transceiver. The holes are smaller when using a foil (solid metal) shield, but foil becomes inflexible with increasing thickness. Thus a thin foil layer is often surrounded by a layer of braided metal, which offers greater flexibility for a given cross-section. The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ...

Although leakage theoretically changes the balance and impedance of a cable, in practice the effect is negligible.

Medium and low-frequency signals can pass through the shield by various means.

External current sources like switched-mode power supplies create a voltage across the inductance of the outer conductor between sender and receiver. The effect is less when there are several parallel cables, as this reduces the inductance and therefore the voltage. Because the outer conductor carries the reference potential for the signal on the inner conductor, the receiving circuit measures the wrong voltage. A switched-mode power supply, switch-mode power supply, or SMPS, is an electronic power supply unit (PSU) that incorporates a switching regulator â€” an internal control circuit that switches power transistors (such as MOSFETs) rapidly on and off in order to stabilize the output voltage or current. ... An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Î¦ through the circuit. ...

The transformer effect is sometimes used to mitigate the effect of currents induced in the shield. The inner and outer conductors form the primary and secondary winding of the transformer, and the effect is enhanced in some high quality cables that have an outer layer of mu-metal. Because of this 1:1 transformer, the aforementioned voltage across the outer conductor is transformed onto the inner conductor so that the two voltages can be cancelled by the receiver. Many sender and receivers have means to reduce the leakage even further. They increase the transformer effect by passing the whole cable through a ferrite core sometimes several times. Figure 1:Three-phase pole-mounted step-down transformer. ... Mu-metal is a nickel-iron alloy (77% nickel, 15% iron, plus copper and molybdenum) that is very efficient for screening magnetic fields. ...

Some senders and receivers use only a limited range of frequencies and block all others by means of an isolating transformer. Such a transformer breaks the shield for high frequencies. Still others avoid the transformer effect altogether by using two capacitors. If the capacitor for the outer conductor is implemented as one thin gap in the shield, no leakage at high frequencies occurs. At high frequencies, beyond the limits of coaxial cables, it becomes more efficient to use other types of transmission line such as glass fibers, which offer low leakage (and much lower losses) around 200 THz and good isolation for all other frequencies. Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...

External low-frequency current sources such as ground loops cause voltages across the resistance of the outer conductor. This problem can be lessened by adding parallel cables to increase the total conductance. To further reduce the problem, the sender and receiver are matched to the cable (see Impedance matching) to minimise currents and their effects in the shield. The term ground loop has more than one meaning: In electrical and electronic engineering, a ground loop refers to an unwanted current that flows in a conductor connecting two points that are nominally at the same potential, for example ground potential, but are actually at different potentials. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Impedance matching is the practice of attempting to make the output impedance of a source equal to the input impedance of the load to which it is ultimately connected, usually in order to maximize the power transfer and minimize reflections from the load. ...

Standards

Most coaxial cables have a characteristic impedance of either 50, 52, 75, or 93 Ω. The RF industry uses standard type-names for coaxial cables. Thanks to television, RG-6 is the most commonly-used coaxial cable, and the majority of connections outside Europe are by F connectors. RG-6/U is a common type of coaxial cable used in a wide variety of residential and commercial applications. ... Male F Connector The F connector is a type of RF connector commonly used for over the air terrestrial television, cable television and universally for satellite television and cable modems, usually with RG-6/U cable or (in older installations) with RG-59/U cable. ...

A series of standard types of coaxial cable were specified for military uses, in the form "RG-#" or "RG-#/U". They go back to World War II and were listed in MIL-HDBK-216 published in 1962. These designations are now obsolete. The current military standard is MIL-SPEC MIL-C-17. MIL-C-17 numbers, such as "M17/75-RG214," are given for military cables and manufacturer's catalog numbers for civilian applications. However, the RG-series designations were so common for generations that they are still used, although critical users should be aware that since the handbook is withdrawn there is no standard to guarantee the electrical and physical characteristics of a cable described as "RG-# type". The RG designators are mostly used to identify compatible connectors that fit the inner conductor, dielectric, and jacket dimensions of the old RG-series cables. Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki TÅjÅ Casualties Military dead: 17,000,000 Civilian dead: 33,000... A United States Defense Standard, often called a military standard, MIL-STD, or MIL-SPEC, is used to help achieve standardization objectives by the U.S. Department of Defense. ... Look up connector in Wiktionary, the free dictionary. ...

Table of RG standards:

type approx. imped. [Ω] core dielectric overall diameter braid velocity factor comments
type [in] [mm] [in] [mm]
RG-6/U 75 1.0 mm PE 0.185 4.7 0.332 8.4 double low loss at high frequency for cable television, satellite television and cable modems
RG-6/UQ 75 PE 0.298 7.62 quad This is "quad shield RG-6". It has four layers of shielding, regular RG-6 only has one or two
RG-8/U 50 2.17 mm PE 0.285 7.2 0.405 10.3 used for thick Ethernet (10base5) and amateur radio
RG-9/U 51 PE 0.420 10.7
RG-11/U 75 1.63 mm PE 0.285 7.2 0.412 10.5 0.66 Used for long drops and underground
RG-58/U 50 0.9 mm PE 0.116 2.9 0.195 5.0 single 0.66 used for radiocommunication and amateur radio, thin Ethernet (10base2) and NIM electronics. Common.
RG-59/U 75 0.81 mm PE 0.146 3.7 0.242 6.1 single 0.66 used to carry baseband video in closed-circuit television, previously used for cable television. Generally it has poor shielding but will carry a HQ HD signal or video over short distances. Not legal for use with any CATV or MATV system.
RG-62/U 92 PE 0.242 6.1 single 0.84 used for ARCNET and automotive radio antennas.
RG-62A 93 ASP 0.242 6.1 single used for NIM electronics
RG-174/U 50 0.48 mm PE 0.100 2.5 0.100 2.55 single common for wifi pigtails, more flexible but higher loss than RG58; used with LEMO 00 connectors in NIM electronics.
RG-178/U 50 7x0.1 mm Ag pltd Cu clad Steel PTFE 0.033 0.84 0.071 1.8 single 0.69
RG-179/U 75 7x0.1 mm Ag pltd Cu PTFE 0.063 1.6 0.098 2.5 single 0.67 VGA RGBHV
RG-213/U 50 7×0.0296 in Cu PE 0.285 7.2 0.405 10.3 single 0.66 for radiocommunication and amateur radio, EMC test antenna cables. Typically lower loss than RG58. Common.
RG-214 50 0.406 10.8
RG-218 50 0.195 in Cu PE 0.660 (0.680?) 16.76 (17.27?) 0.870 22 single 0.66 large diameter, not very flexible, low loss (2.5dB/100' @ 400MHz), 11kV dielectric withstand.
RG-223 50 2.74mm FE .285 7.24 .405 10.29 Double
RG-316/U 50 7×0.0067 in PTFE 0.060 1.5 0.102 2.6 single used with LEMO 00 connectors in NIM electronics

type approx. imped. [Ω] core dielectric overall diameter braid velocity factor comments
type [in] [mm] [in] [mm]
H155 50 0.79 lower loss at high frequency for radiocommunication and amateur radio
H500 50 0.82 low loss at high frequency for radiocommunication and amateur radio
LMR-195 50 low loss drop-in replacement for RG-58
LMR-200 HDF-200 CFD-200 50 1.12 mm Cu PF CF 0.116 2.95 0.195 4.95 0.83 low loss communications, 0.554 dB/meter @ 2.4 GHz
LMR-400 HDF-400 CFD-400 50 2.74 mm Cu clad Al PF CF 0.285 7.24 0.405 10.29 0.85 low loss communications, 0.223 dB/meter @ 2.4 GHz
LMR-600 50 4.47 mm Cu clad Al PF 0.455 11.56 0.590 14.99 0.87 low loss communications, 0.144 dB/meter @ 2.4 GHz
LMR-900 50 6.65 mm BC tube PF 0.680 17.27 0.870 22.10 0.87 low loss communications, 0.098 dB/meter @ 2.4 GHz
LMR-1200 50 8.86 mm BC tube PF 0.920 23.37 1.200 30.48 0.88 low loss communications, 0.075 dB/meter @ 2.4 GHz
LMR-1700 50 13.39 mm BC tube PF 1.350 34.29 1.670 42.42 0.89 low loss communications, 0.056 dB/meter @ 2.4 GHz

References for this section

• RF transmission lines and fittings. Military Standardization Handbook MIL-HDBK-216, U.S. Department of Defense, 4 January 1962. [1]
• Withdrawal Notice for MIL-HDBK-216 2001
• Cables, radio frequency, flexible and rigid. Details Specification MIL-DTL-17H, 19 August 2005 (superseding MIL-C-17G, 9 March 1990). [2]
• Radio-frequency cables, International Standard IEC 60096.
• Coaxial communication cables, International Standard IEC 61196.
• Coaxial cables, British Standard BS EN 50117
• H. P. Westman et al, (ed), Reference Data for Radio Engineers, Fifth Edition, 1968, Howard W. Sams and Co., no ISBN, Library of Congress Card No. 43-14665
• http://www.rfcafe.com/references/electrical/coax_chart.htm
• Times Microwave Systems LMR Wireless Products Catalog
• CFD Cable Specifications
• Specs of RG174/U, RG58C/U etc.
• RG213/8, RG218, CLX1/4", CLX1/2", CLX7/8", CLX1+5/8" Cable Power & Impedance Specs
• Velocity factor of various coaxial cables

The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... The International Electrotechnical Commission (IEC) is an international standards organization dealing with electrical, electronic and related technologies. ... British Standards is the new name of the British Standards Institute and is part of BSI Group which also includes a testing organisation. ...

Significance of impedance

A question that is often asked is what the significance of a 52 or 75 Ω characteristic impedance is. The best coaxial cable impedances to use in high-power, high-voltage, and low-attenuation applications were experimentally determined in 1929 at Bell Laboratories to be 30, 60, and 77 Ω respectively.[citation needed] 30 Ω cable is exceedingly hard to make however, so a compromise between 30 Ω and 60 Ω was reached at 52 Ω, which has persisted; note this also corresponds very closely to the drive impedance of a half wave dipole antenna in real environments, and provides an acceptable match to the drive impedance of quarter wave monopoles as well. 73 Ω is an exact match for a centre fed dipole aerial/antenna in free space (approximated by very high dipoles without ground reflections), so 75 was adopted as a compromise between 73 and 77 ohms. The characteristic impedance of a uniform transmission line is the ratio of the amplitudes of a single pair of voltage and current waves propagating along the line in the absence of reflections. ... Bell Telephone Laboratories or Bell Labs was originally the research and development arm of the United States Bell System, and was the premier corporate facility of its type, developing a range of revolutionary technologies from telephone switches to specialized coverings for telephone cables, to the transistor. ...

Uses

Long distance coaxial cable is used to connect radio networks and television networks, though this has largely been superseded by other more high-tech methods (fibre optics, T1/E1, satellite). It still carries cable television signals to the majority of television receivers, and this purpose consumes the majority of coaxial cable production. A radio network is a network system which distributes programming to multiple stations simultaneously, or slightly delayed, for the purpose of extending total coverage beyond the limits of a single broadcast signal. ... A television network is a distribution network for television content whereby a central operation provides programming for many television stations. ... Fiber Optic strands An optical fiber in American English or fibre in British English is a transparent thin fiber for transmitting light. ... Two Network Interface Units, one with a single card, the other with two In telecommunications, T-carrier is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America and Japan. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... For other uses, see Satellite (disambiguation). ... Coaxial cable is often used to transmit cable television into the house. ...

Micro coaxial cables are used in a range of consumer devices, military equipment, and also in ultra-sound scanning equipment.

Types

RG/6 is available in three different types designed for various applications. "Plain" or "house" wire is designed for indoor or external house wiring. "Flooded" cable is infused with heavy waterproofing for use in underground conduit. "Messenger" contains some waterproofing but is distinguished by the addition of a steel messenger wire along its length to carry the tension involved in an aerial drop from a utility pole.

Triaxial cable or triax is coaxial cable with a third layer of shielding, insulation and sheathing. The outer shield, which is earthed (grounded), protects the inner shield from electromagnetic interference from outside sources. Triaxial Cable is a type of electrical cable similar to coaxial cable, but with the addition of an extra layer of insulation and a second conducting sheath. ...

Twin-axial cable or twinax is a balanced, twisted pair within a cylindrical shield. It allows a nearly perfect differential signal which is both shielded and balanced to pass through. Multi-conductor coaxial cable is also sometimes used.

Biaxial cable or biax is a figure-8 configuration of two 50 Ω coaxial cables, used in some proprietary computer networks. For the scientific and engineering discipline studying computer networks, see Computer networking. ...

Semi-rigid cable is a coaxial form using a solid copper outer sheath. This type of coax offers superior screening compared to cables with a braided outer conductor, especially at higher frequencies. The major disadvantage is that the cable, as its name implies, is not very flexible, and is not intended to be flexed after initial forming.

Interference and troubleshooting

Coaxial cable insulation can degrade requiring cable replacement, especially if it has been exposed to the elements on a continuous basis. The shield is normally grounded, and if even a single thread of the braid or filament of foil touches the center conductor, the signal will be shorted causing significant or total signal loss. This most often occurs at improperly installed end connectors and splices. Also, the connector or splice must be properly attached to the shield, as this provides the return electrical path for the signal.

Despite being shielded, interference can occur on coaxial cable lines. Susceptibility to interference has little relationship to broad cable type designations (e.g. RG-59, RG-6) but is strongly related to the composition and configuration of the cable's shielding. For cable television, with frequencies extending well into the UHF range, a foil shield is normally provided, and will provide total coverage as well as high effectiveness against high-frequency interference. Foil shielding is ordinarily accompanied by a tinned copper or aluminum braid shield, with anywhere from 60 to 95% coverage. The braid is important to shield effectiveness because (1) it is more effective than foil at absorbing low-frequency interference, (2) it provides higher conductivity to ground than foil, and (3) it makes connectorization easier and more reliable. "Quad-shield" cable, using two low-coverage aluminum braid shields and two layers of foil, is often used in situations involving troublesome interference, but is less effective than a single layer of foil and single high-coverage copper braid shield such as is found on broadcast-quality precision video cable. Coaxial cable is often used to transmit cable television into the house. ...

In the United States and some other countries, cable channels 2-13 share the same frequency as those from television broadcast towers. If the cable consumer is too close to a television tower and the cable company provides the same station on the like channel, interference and 'ghosting' may result. One solution is to make sure the cable signal is at the maximum allowed strength (especially if splitters are used for multiple TV sets), as this will increase the signal-to-noise ratio (the "noise" being the pickup of the broadcast tower). Choosing coaxial cable with high shield effectiveness, and ensuring that connections are sound and tight, can also help reduce interference. Only industrial-quality cable TV amplifiers (generally not available at retail) should be used to amplify weak signals. Cheaper ones, sold at consumer electronics stores, often cause more problems than they solve. A hybrid coil (or bridge transformer) is a single transformer that effectively has three windings, and which is designed to be configured as a circuit having four branches, (i. ...

Timeline

overhead radio frequency power transmission line at Solec Kujawski longwave transmitter, Solec Kujawski, Poland Radio frequency power transmission is the transmission of the output power of a transmitter to an antenna. ... L-carrier was the Bell System designation for analog Long distance frequency-division multiplexing transmission systems using co-axial cable. ... Transmission lines are generally unbalanced or balanced. ...

Results from FactBites:

 Coaxial Cable: Teledatacom Glossary (179 words) Coaxial cable is the kind of copper cable used by cable TV companies between the community antenna and user homes and businesses. Coaxial cable is sometimes used by telephone companies from their central office to the telephone poles near users. Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis.
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